The present invention relates to an optical disc discriminating apparatus for enabling reproduction of a plurality of optical discs different in track pitch by an optical disc player.
At present, two types of optical discs, which are the same in substrate shape and reflectance of a signal recording surface but different in track pitch, have been proposed. One of them is a compact disc (CD), and the other is a digital versatile (video) disc (DVD) that is a high-density optical disc. The track pitch of the former is 1.6 .mu.m, and that of the latter is 0.74 .mu.m, which respectively require a separate tracking servo system. Two types of reproducing mechanisms are essentially necessary in order to reproduce the two types of discs. However, recently, an optical disc player having the reproducing function of both the optical discs has been demanded in consideration of a user's burden.
A disc player for reproducing two different types of discs is disclosed, for example, in Japanese Patent Laid-Open No. 1994(6)-68506.
According to the technique disclosed in the aforementioned Publication, a laser beam is irradiated onto a track pitch identifying information indicating portion on the optical disc on which information relating to the track pitch is recorded. A laser beam reflected from the track pitch identifying information portion is detected to discriminate between optical discs different in track pitch to control tracking servo according to the identified track pitch.
As described above, in the conventional arrangement, the tracking servo according to the respective track pitches are necessary to reproduce two types of discs, but the type of the optical discs need be discriminated in advance in order to switch the two types of tracking servo methods. However, at present, since the substrate shape of the disc and the reflectance of the signal recording surface are the same, the discrimination prior to application of the tracking servo is difficult.
Further, in the technique disclosed in the aforementioned Publication, it has been necessary that for discriminating between the optical discs different in track pitch, as a track pitch identifying information portion, a groove is provided between a signal recording area of the disc and a chucking hole provided in the center of the disc for holding the disc, or a flat mirror surface is provided in the periphery of the chucking hole, so that the intensity of laser beams reflected from the track pitch identifying information portions are differentiated according to the types of the optical discs.